For the sintered WC-Co alloys of different microstructure, domain size and root mean squared strain of the WC phase and residual stress in the WC and Co phases were measured on the ground and annealed surfaces by means of X-ray diffraction method. With varying of the microstructure the root mean squared strain and the domain size in the ground surface changed in a given range. The root mean squared strain decreased linearly with an increase of annealing temperature and settled down to about 1.4×10^-3 at a given rate, independent of the microstructure. The recrystallization temperature of WC phase in the alloys lowered with an increase of the Co-content between 800 and 1000°C, while the hot-pressed WC recrystalized at 1200°C. The maximum residual stress of about 2.5 GPa in the WC phase in ground surface, was found in a fine grained WC-6wt%Co alloy. The residual stress was almost released by removing Co from the surface layer or by annealing at 800°C, which was considerably lower than the annealing temperature of (1000-1200°C) for stress-relief in the hot-pressed WC.